1. Field of the Invention
The present invention is generally related to forklifts including distributed control systems, more particularly, to cooperative control using distributed control systems within forklifts.
2. Description of the Related Art
Recently, an increasing number of engine-driven vehicles, including forklifts and construction machines, adopt electronic control systems. Electronic control systems use stored computer programs and control data for controlling respective devices within vehicles.
One requirement of recent forklifts is reduction in size of control systems. Recent advance in forklifts components requires control systems to be highly specified, and this leads to increase in the number of signal cables, and also increase in the size of the control systems. Increase in the size of control systems is undesirable, especially for size-reduced forklifts.
Another requirement is improved flexibility and adaptability of control systems. Control systems are often required to be dedicatedly designed, because functions of forklifts may be different depending on models or installed options. Additionally, in order to modify the performance of forklift components, the computer programs and control data often need to be modified for adapting operational environments of forklifts. A highly adaptable control system is one solution for providing various dedicated controllers and highly adapting operational environments.
U.S. Pat. No. 5,687,081 discloses a lift track control system with improved adaptability. The disclosed control system is composed of control modules which are software configurable and can receive software from a removable programmable cartridge. The control modules allows the hardware component of the control system to be mounted on a wide range of the lift track, then configured with boot and application software appropriate for the specific model and associated accessories.
Additionally, Japanese Laid Open Patent Application (JP-A-Heisei 10-280488) discloses a construction machine including a distributed controller. The architecture of the construction machine is capable of failure diagnosis of the distributed controller. The distributed controller includes input/output controllers, and a main controller provided with failure diagnosis means for detecting failure of the input/output controllers. The failure diagnosis means monitors data received from the input/output controllers, and determines that a specific input/output controller experiences failure when not receiving data from the specific input/output controller for a given period.
Furthermore, Japanese Laid Open Patent Application (JP-A-Heisei 10-276509) discloses a sub-controller configured to provide interface between tractor accessories and a tractor controller unit for reducing the number of input/output terminals of the tractor controller unit. The sub-controller is composed of a communication interface for communication of the tractor controller unit, a CPU which processes signals received from the tractor controller unit, a RAM card used for storing work data obtained through the signal processing, and an output interface for driving motors of the tractor accessories.
Japanese Laid Open Patent Application (JP-A-Heisei 8-253956) discloses an electrical control system of a construction machine for improving flexibility of the system, vibration and noise tolerances, and ease of maintenance. The electrical control system is composed of three or more controllers configured to control a hydraulic system to operate the construction machine. One of the controllers is used as a main controller, and remainders are grouped into first and second groups. The controllers of the first group receive signals from input devices and sensors to develop control data. The controllers of the second group generate drive signals to operate components of the hydraulic system in response to the control data received from the first group of controllers. The main controller manages the controllers of both of the first and second groups.
Japanese Laid Open Patent Application (JP-A-Heisei 11-81392) discloses an automatic construction machine for improving safety and unit protection. The automatic construction machine is composed of a plurality of controllers connected through a LAN. The plurality of control includes a safety/protection controller. The safety/protection controller is connected to a remainder of controllers through another independent network. The safety/protection controller exchanges safety/protection signals through both the LAN and the independent network.
Finally, Japanese Laid Open Patent Application (Jp-A-2001-328800) discloses a control system suitable for industrial machines for reducing the size, cost, and influences caused by failure of the system. The control system is composed of a plurality of controllers connected through a network. The structure of the control system in the time domain includes a plurality of operation modes. The controllers are associated with the operation modes, and configured to achieve desired control when the control system is placed in the associated operation modes. This architecture eliminates a need for providing a mode controller, and this effectively reduces the size and cost of the system.